Pump or compressor



April 13, 1948. A. A. MERCER PUMP OR COMPRESSOR Filed April 3, 1944 3 sheets-sheet n 1 ,I u N Abitur/ley l April 13, 1948;` A. A. MERCER 2,439,568

PUMP 0R COMPRESSOR Filed April 3, 1944 Sheets-Sheet 2 `Fui-4.

` Inventor 2O Mull, By Y P `t j Attorney l April 13, 1948.

A. A. MERCER VPUMP on cournsson Filed April, s, 1944 :s sheets-smet s j I: l nvell'flor Attorney PatentedApr. A413, 1948 Arthur Alexander Mercer,

asslgnor of ten per cent to chester, England Colchester, England, lernard Mason, Col- Application April 3,1944, Serial N0. 529,293 lIn Great Britain April 21,1943

s claims. (ci. s-isz) This invention relates to pumps (or compressors) of the kind comprising a closed cylindrical casing having diametrically opposed inlet and deliveryv ports at its medial plane, a rotor in the casing having a plurality of cylinders extending through it parallel to its axis of rotation and a port extending radially outwards from each cyl- 4inder to register periodically with th'e said inlet and delivery ports, a shaft for driving the rotor.

and a pair of opposed plungers reciprocable in each of said cylinders as the rotor rotates.

An object of the invention is to devise a pump of this kind, for xed or variable delivery according to requirements, which is of improved and simplified construction not requiring complicated and costly machinery or assembling operations, and in which such wear as is reasonable is confined to easily replaceable parts.

To the attainment of this object the invention provides in a pump of the stated kind the combination of two normally stationary end rings each presenting a circular cam track, and portions at the outer ends of the opposed pairs of plungers shaped to embrace the said tracks', whereby the opposed plungers are positively and mechanically displaced on both their outward and inward strokes as the pump rotor rotates in a smooth manner without danger of impact shocks and resultant wear and noise. Preferably. the plungers are shaped, at their outer ends, to afford shoulders or necked portions that embrace the circular tracks presented by the said end rings.

The said circular tracks may be curved to' bring about, during each complete rotation of the pump rotor, outwarddisplacement of each pair 0f opposed plungers while they pass th'e inlet port in the casing, followed by a period of axial immobility, followed by inward displacement while they pass the delivery port in the casing, followed by a second period of axial immobllity until the beginning of the next cycle.l However. and especialiy for high speed pumps, the two end rings may present plane circular tracks disposed obliquely to kthe axis of the rotor and embraced by the shaped portions of the plungers as aforesaid.

Variable rate of delivery of the pump can be obtained by providing either for axial displacement of the rotor thereby at least partially to mask the rotor ports while they traverse the inlet and delivery zones of the stator, or for angulai` displacement of the end rings simultaneously in opposite directions to alter the timing of the iluid inlet and delivery at each cycle. x

Simple manually controllable means for axially section,

2 displacing the rotor comprises a threaded shaft screwed into one of the end covers of the pump casing and having a head engaging a counter bore in the rotor in such manner that whilst the roto'r .is free to rotate relatively to the threaded shaft.

any axial displacement of the latter (by screwing it in the aforesaid end cover) results in a corresponding Kaxial displacement ofthe rotor.

On the other hand, simple `manually controlla'ble means for angularly displacing the end rings as and for `the purpose stated comprises a pair of aligned pinion shafts mounted. in the pump casing parallel to the rotor, bevel wheels connecting the inner ends of the pinion shafts to a manual control shaft projecting engaging teeth' formed externally on the end rings or on turnable carriers accommodating the same.

By way of non-limitative example some constructional forms of pumps embodying the recited features of the invention are illustrated by the accompanying drawings, whereon:

Figs. 1 and 2 show one form embodying proilled end cams, Fig. l. representing a horizontal axial and Fig. 2 a medial cross section in the plane II-II of Fig. 1;

Fig. 3 is a similar view to Fig. 1 of another form embodying profiled end cams, the pump drive shaft being omitted;

Fig', 4 represents a horizontal axial section of a, form embodying plane, obliquely disposed cams;

Fig. 5 represents'a vertical axial section of another-,form embodying plane, obliquely disposed cams, and sh'ows means for manually turning the cam carriers to alter the setting of the cams; and

Fig. 6 shows in horizontal axial section a form which embodies an internal circulatory system for a coolant and lubricant.

Referring iirst generally to the several figures of the drawings, Whereon the same references are used throughout to denote the same or similar parts, i isl an open-ended cylindrical casing or stator with 'diametrically opposite inlet and delivering branches 2 and 3, 4 a Wear resisting stator lining with inlet and delivery ports 5 and 8. 'l `a rotor having a central bore 8 and any desired number of open-endedcylinders 9 equally spaced apart near its periphery with their axes parallel to that of the rotor, l0 a rotor drive shaft, l2

plungers slidable in the cylinders, `l3 end covers for the casing, and I4 end ring members presenting cams or wipersthat coact with the plungers. These plungers are each pai;` is slidable in one of the cylinders 9, i. e.,

from the casing, and gear wheels at the outer ends of the pinion shafts grouped in opposed pairs andv tracks I1 embraced by U-shaped heads 3 each cylinder in the single rotor I is common to two opposed plungers I2, I2. V

Referring now particularly/to Figs. 1 and 2, the rotor 1 is splined, at II, to the co-axial drive shaft I0, which is .Iournalled in one of the end covers I3`for the casing I, so that it is compelled to rotate with the shaft but isfree to slide axially thereon within the "stator lining 4. bearing rollers I8 being provided between the rotor and the lining. The two end rings I4, I4 are fixedly clamped, onebetween each end of the stator and the' pertaining end cover I3; they present cam I3 formed integral with the outer ends of the opposed pairs of plungers I2, I2. They plunger heads I8 bear on hardened sleeves I9, I9 carried by the internal bosses of the encl covers I3, I3 and they engage This arrangement simpliilesithe machining of the thel cam tracks through the intermediary of anti-' friction bearings 20, 20.

A fluid space is afforded in each cylinder 9 between the two oppositely movable plungers I2, I2 therein and from this space each cylinder has a radial port 2Iy (see Fig. 2) opening to the periphery of the rotor 1 and adapted to register with the stator inlet and delivery ports 5 and 6. As will be evident from the illustration, the arrangement is such that at any instant in the rotation of the rotor 1 a number of cylinders 9 will be open to suction with their opposed plungers at various stages of outward movement, a number will be open to delivery with their opposed plungers at various stages of inward movement, and the remaining cylinders will be masked or closed by the stator lining 4.

When the shaft I0 is rotated, the rotor 1 is also rotated together with the plungers I2. Then, owing to the operative connection between the opposed plunger heads I8 I8 and the cam tracks I1, I1 afforded by the fixed end cam rings I4, I4 the plungers are axially displaced in the rotor cylinders 9, and'since they move in opposite directions inA pairs the fluid space between them is .repeatedly varied to a constant extent. Obviously, the/cam tracks are so profiled and so related t0 the inlet and the opp'sed plungers move apart while passing outlet ports aforesaid that' the inlet port 5 and towards one another while passing the delivery port 6. While passing over from inlet to delivery and from delivery to inlet,v,

no axial movement of the plungers occurs, the cam tracks being profiled to bring about these dwells.

' A threaded shaft 22 (Fig. 1) is screwed into a screw-threaded bore in one of the end covers I3;

it `carries a ball bearing 23 whose outer race fits Va slight enlargement in one end of the central bore 3 in the rotor 1. Thus, the rotor is free to turn relative to the threaded shaft 22, but by turning the threaded shaft and thereby displacing it axially the rotor is also displaced axially, tb shift the ports 2| of the rotor cylinders 9 partly or wholly from coincidence with the inlet and delivery ports 5 and 6 in the stator lining and so vary the pump delivery. If desired and to ensure a fine degree of adjustment of delivery, the ports 2I may be circumferentially staggered or offset.

Passing now to Fig. 3, the pump there shown is very similar to that of Figs. 1 and 2, the chief nuts-21, 21 screwed on the shaft.

plungers. The cam tracks and recess are profiled the same as the cam tracks 20, 20 of the pump according to Figs.v 1 and 2, and the operation of both forms of pump is similar. That of Fig. 3 is, however, a fixed delivery pump, no provision being made for axially displacing the rotor.

In the constructional form of the pump shown by Fig. 4 the rotor drive shaft I0 extends .right through the pump casing I and is journalle'd by means of thrust ball races 26, 26 retained by The casing end covers I3, I3 are equipped with sealing caps 28, 23. In this instance the ring members I4, I4 are turnably mounted, aboutithe rotor axes, between the end covers and the ends of the stator lining 4; each of them presents a. plane, inclined cam track 20'embraced by necked portions 23 at the outer ends of the plungers I2, and an undercut recess wherein is located an obliquely set ball bearing 29 whose inner race is engaged by the spherical outer ends I5 of the plungers. The reactionary forces from the plungers are trans ferred through the carrier rings and the ball bearings to the drive shaft, this arrangement being especially suitable for heavy duty pumps. During the operation of the pump the ring members I4, I4v do not rotate, but under the outward ball bearings 29 may turn with the plungers, an arrangement which reduces wear. Since the tracks 20, 20 are plane oblique flanges there will be no period ofv axial immobility of the opposed pairs of plungers I2, I2 which at each rotation of the rotor will move without pause outwardly from one another and then inwardly towards one another.'

Variable rate' of delivery of the pump` is ob` tained by turning the ring members I4, I4 simultaneously in opposite directions, thereby to vary the distances apart of the opposed plungers as they pass the pump inlet and outlet zones. To this end the ring members have external gear teeth 30, 30 and, as is shown in the embodiment illustrated by Fig. 5, two shafts 32, 32 journalled in the pump casing I have spur gears 3l, 3| engaging these teeth; moreover the two shafts also have gear 34 on a manually turnable shaft 35 extending from the casing. y

Substantially the only difference between the embodiment of the pump shown by Fig. 5 and that of Fig. 4 is` in the manner of mounting the rotor drive shaft I0. In Fig. 5 Journal ball races 26a, 26a are employed, and the shaft end caps contain knownoil sealing means 36, 36. InFig. 5 can also be seen ducts 31, 31 for connection to a supply of lubricant.

Inthe embodiment of the invention illustrated by Fig. 6, the cam or wiper mechanism for ensuring reciprocation of the opposed pairs of plungers I2, I2 when the rotor 1 is driven and the mechanism for' manually varying the rate of delivery is identical with those of the forms of the pump already described with reference to Figs. 4 and 5. Here, however, provision is made for circulating a lubricating and cooling medium continuously through the interior of the pump. As shown the drive shaft I0 is connected to the rotor 1 by two sets of splines I I, II, those of one set being displaced or oiset with respect to the other to afford a through passage for the medium. `The drive shaft also has mounted thereon helical impeller vanes 33, 38. The ball races 26a, 26a in which the drive shaft is journalled are contained bevel gears 33, 33 which mesh with a bevel in housings aiorded by members 39, 39 to which are secured the shaft end caps 28, 28 containing the seals 3B, 36. These members 39, 39 are formed with tubular branches 40, 4D adapted to be connected to an external closed circuit (not shown) for the lubricating and cooling medium. VIt will be evident that with this arrangement the impellers 33, 38 will cause a through now of the medium which has free access to parts within the pump casing.

The entire pump in each of the vforms described and illustrated is constituted by few working parts under elimination of valves, and the machining of the said parts consists almost entirely ofstraightforward turning operations. lThe end thrusts of the opposed piungers are balanced, so that neither the rotor nor the rotor drive shaft is subjected to end thrusts from which follows that wear of the pump parts is reduced to the lrninin mum. In fact substantially the entire wear occurs on the piunger heads, and the plungers presenting these heads are easily renewable at small cost. There are no springs or equivalent ineinhers iikeiy to cause trouble, the plungers being positively reciprccated, smoothly and without noise, by the cam or wiper tracks which their outer ends embrace. i

It is to be observed that cam rings remain stationary during the operation of the pump and that the reciprocating plungers rotate with the rotor and its drive shaft but without these latter being subjected to end thrusts.

Pumps in accordance with the invention may be used for divers ed, for instance, for the fuel internal combustion injection systems of engines, and for hydraulically operated mechanisms on aircraft and machine tools.

I clailn: A 1. Ina pump of the rotor in the casing having a plurality of cylinders extending therethrough parallel to its axis of rotation, and a port extending radially outwards from each cylinder to register periodically with thesaid inlet and delivery ports, a shaft for driving the rotor, and a, pair of opposed plungers reciprocable in each of the said cylinders as the rotor rotates; the combinationof means for positively and mechanically displacing the opposed plungers -on both their outward and inward strokes, said means comprising two normally stationary end rings each presenting a circular cam track, and portions at the outer ends of the opposed plungers shaped to embrace the said tracks;`and means for varying the delivery by partially4 masking the rotor ports comprising a shaft screw-threaded in the pump casing, and a head on the shaft engaging a counterbore in the rotor whereby the rotor is axially displaced by turning the said shaft.

2. In a pump of the kind comprising a closed cylindrical casinghaving diametrically opposed inlet and delivery ports at its medial' plane, a rotor in the casing having a, plurality of cylinders extending therethrough parallel to its axis of rotation, and a port extending radiallyoutwards from each cylinder to register periodically with the said inlet and delivery ports, a shaft for driving the frotor, and a pair reciprocable in each of the said cylinders as the rotor rotates; the combination of means for positively and mechanically displacing the opposed plungers on both their outward and inward `the working l purposes. They are'well adaptv kind comprising a closed A cylindrical casing having 'diametrlcally opposed inlet and delivery ports at its medial plane, a

strokes, said means comprising two normally stationary end rings each presenting an inclined thrust race andspaced therefrom a circular cam track, rounded heads at the outer ends of the opposed plungers to abut said thrust races and necked portions adjacent said heads to embrace the said tracks; and means for varying the delivery by partially masking the rotor ports com prising a shaft screw-threaded in the pump casing, and a head on the shaft engaging a counterbore in the rotor whereby the rotor is axially displaced by turning the said shaft. l

3. In a pump of the kind comprising a closed cylindrical casing having diametrically opposed inlet and delivery ports at its medial plane, a rotor in the casing having a plurality'of cylinders extending therethrough parallel to its axis of rotation, and a port extending radially outwards dit . posed plungers while they` ends of the opposed plungers to of opposed plungers from each cylinder to register periodically with the said inlet and delivery ports,- a shaft for driving the rotor, and pair of opposed plungers re ciprocahle in each of the said cylinders as the rotor rotates; the combination of means for positively and mechanically displacing the opposed plungers on both their outward and inward strokes, said means comprising two `normally stationary end rings each presenting a, circular cazntrack, and portions at opposed plungers shaped to embrace the said tracks, the said tracks being profiled to bring about, during each complete rotation of the: rotor, outward axial displacement of each pair of oppass the inlet port in the casing, followed by` a period of axial immobility, followed by inward displacement while they pass the delivery port in the casing, foln lowed by a second period of axial immobility until the beginning of the next cycle; and means for varying the delivery by partially masking the rotor ports comprising a in the pump casingrand'a head on the shaft engaging a counterbore in the rotor whereby the rotor is axially displaced byY turning the said shaft.

4. In a pump of the kind comprising a closed inlet and delivery ports at its medial plane, a rotor in the casing having a plurality of cyllnders extending therethrough parallel to its axis of rotation, and a port extending radially outwards from each cylinder 'to register periodically with the said inlet and delivery ports, a shaft for driving the rotor, and a pair of opposed plungers reciprocable in each of the said cylindersas the rotor rotates; the combination of means for positively and mechanically displacing the opposedplungerson both their outward and inward strokes, said means comprising two normally stationary end rings each presenting an inclined thrust race and spaced therefrom a circular cam track, rounded heads at the outer abut said thrust races and necked portions adjacent said heads to embrace the said tracks, the said tracks being profiled to bring rotation of the rotor, outward axial displacement of each pair of opposed plungers while they pass the inlet port in the casing, followed by a period of axial immobility, followed by inward displacement While they pass the delivery port in the casing, followed by a second period of axial im- Amobility until the beginning of the next cycle;

the outer ends of theabout, during each complete shaft screw-threaded i and means for varying the delivery by partially masking the rotor shaft screw-threaded in the pump casing, and

ports comprising a l a head on the shaft engaging a counterbore in the rotor wherebyl the rotor is axially displaced by turning the said shaft.

5. In a pump of the kind comprising a closed cylindrical casing having diametrically opposed inlet and delivery ports atits medial plane, a rotor in the casing having a plurality of cylinders extending therethrough parallel to its axis of rotation, and a port extending radially out-v the said tracks; and means for varying the de-r the two end said livery rate by angularly displacing rings simultaneously in opposite directions,

' means comprising a pair of aligned pinion shafts mounted in the pump casing parallel to the rotor,

a manual control shaft projecting from the cas-l ing, bevel. wheels connecting the irmer ends of 'the pinion shafts with the control shaft, and

gear wheels at the outer ends of the pinion shafts engaging teeth formed externally on the end rings.

6. In a pump of the kind comprising a closed cylindrical casing having diametrically exposed inlet and delivery ports at its medial plane, a rotor in the casing having a plurality of cylinders extending therethrough parallel to its axisof rotation, and a 4port extending radially outwards from each cylinder to register periodically lwith the said inlet and delivery ports, a shaft for driving the rotor. and a pair of opposed plungers reciprocable in each of the said cylin ders as the rotor rotates; the combination of means for positively and mechanically displacing Y the opposed plungers on both their outward and l inward strokes, said means comprising two normally stationary end rings each presenting an inclined thrust race and spaced'therefrom a circular cam track, rounded heads at the outer ends of the opposed piungers to abut said thrust races .and necked portions adjacent said heads to embrace the said tracks; and means for varying the delivery rate by angularly displacing the two end rings simultaneously in opposite directions. said means comprising a pair o f `aligned pinion shafts mounted in the pump casing parallel to the rotor, a manual control shaft projecting from the casing..bevel wheels connecting the inner ends of the pinion shafts with the control shaft, and gear wheels at the outer end of the pinion shafts engaging teeth formed externally on the end rings. ARTHUR ALEXANDER MEREER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,180,190 Robertson Apr. 18, 1916 1,287,026 A Janney Dec. 10, 1918 1,669,976 De Leeuw May 15, 1928 2,095,255 Holmes Oct. 12, 1937 2,192,539 Condon Mar. 5, 1940 FOREIGN PATENTS Number Country. v y Date 40,221 Denmark 1929 293,801 Great Britain Mar. 28', 1929 851,663 yFrance oct.` 9, 1939 

